1. Field of the Invention
This invention relates to devices and methods for determining the amount of alcohol in a person's breath, and more particularly to the retention of the alcohol for later evaluation.
2. Description of the Prior Art
The adsorption of alcohol from a gas such as air may be important for a variety of reasons. A primary application is in the field of law enforcement, in which breath analysis devices are used to test alcohol content of a person's breath.
Breath analysis devices of various types are known in the art. In the apparatus known as the "Breathalyzer", a 521/2 ml. sample of breath is collected in a heated reservoir and is then bubbled through an ampoule containing a solution of potassium dichromate in a 50% aqueous sulfuric acid solution. The alcohol content is determined by photometric measurement of the reduction of the dichromate by alcohol. Comparable devices are disclosed in U.S. Pat. No. 3,544,273, issued to McConnaughey on Dec. 1, 1970; U.S. Pat. No. 3,303,840, issued to Etzlinger on Feb. 14, 1967; and U.S. Pat. No. 3,238,783, issued to Wright on Mar. 8, 1966. The specification in the McConnaughey patent discloses a representative operation of these types of devices, and is hereby incorporated by reference. In the McConnaughey apparatus, the breath sample is passed through a tube containing a chromium compound held between glass wool plugs. The chromium compound changes color in response to alcohol in the breath sample. This and other prior art devices for analysis of breath alcohol uniformly incorporate a chemical reagent which reacts to the alcohol, rather than retaining it for later assaying.
Some compounds are known to adsorb certain other materials. Calcium sulfate has been recognized to be a desiccant substance which will adsorb water from air or other materials. This property is disclosed in U.S. Pat. Nos. 2,813,010, issued to Hutchins on Nov. 12, 1957; U.S. Pat. No. 2,758,719, issued to Line on Aug. 14, 1956; and, U.S. Pat. No. 2,593,132, issued to Gannon on Apr. 15, 1952. Calcium sulfate has also been used to remove water from alcohol in order to concentrate the alcohol, as is described in Volume 14, pages 34-37 of the Transactions of the Indiana Institute of Chemical Engineers (1961-1962) and pages 16-21 of Chemical Process Design, Symposium, Bangalore, Indiana (1963). These sources, however, do not disclose the property of calcium sulfate to adsorb alcohol itself from air or a similar material.
Other known desiccants include calcium chloride, magnesium sulfate, sodium sulphate and silica gel, as disclosed in U.S. Pat. No. 1,789,194, issued to Rockwell on Jan. 13, 1931; and the Hutchins patent and publications previously cited. These sources do not discuss the potential for any of these desiccants to adsorb alcohol. However, it has been known to use magnesium perchlorate and calcium chloride to retain breath alcohol for later assaying.
In the use of various desiccants, a number of containers have been devised to contain the desiccant. The Rockwell device utilizes a cannister in which a spring bearing against the cannister top holds a screen against a cotton pad which contacts the desiccant. A similar structure is described in U.S. Pat. No. 2,575,483, issued to Bethig on Nov. 20, 1951, and in the Gannon and Line patents previously cited. The use of a pad, glass wool, paper and/or a screen positioned adjacent a desiccant is disclosed in U.S. Pat. No. 3,008,540, issued to Gibson on Nov. 14, 1961; U.S. Pat. No. 2,682,315, issued to Evans on June 29, 1954; U.S. Pat. No. 2,225,990, issued to Henry on Dec. 24, 1940; and U.S. Pat. No. 1,585,113, issued to Robert on May 18, 1926; and also in the Hutchins and Line patents discussed previously. None of these patents however, disclose a structure which is simply constructed for retaining a small portion of material and which permits the contents to be readily discharged for further treatment.